A Life-cycle Autonomous Modular System for Aircraft Material State Evaluation and Restoring System

Final Report Summary - ALAMSA (A Life-cycle Autonomous Modular System for Aircraft Material State Evaluation and Restoring System)

Executive Summary:
The project ALAMSA proposed an autonomous modular system for Material State Evaluation and Restoring System (MSERS) of aircraft structures leading to an initial assessment of the continuous known (and restored) material health and demonstrate its efficiency in a life-cycle simulated environment starting from the production to a laboratory environment.
Novel Non-destructive Technique and Structural Health Monitoring imaging concept based on nonlinear acoustics were successfully developed and tested on simple samples and components. These methods were capable of recognising and imaging clear with structural changes, allowing future aircraft maintenance operators of the need of a repair intervention.
These "intelligent" automatic self-monitoring system, were connected to novel in-situ “self-repair” capability with the aim to actively re-establish the continuity and integrity of the damaged area. Repair systems based on self-healing concepts were developed. In particular, novel self-repair mechanisms were investigated based on using thermally activated healing thermoset as a matrix based on the Diels Alder cycloaddition reaction and employing a novel type of composites using doped ionomers as the polymeric matrix, which also heal upon temperature application. These thermally reversible polymers were capable of closing internal cracks through an ad-hoc activated shape memory effect or pressure that allows re-cohesion of surface cracks upon a thermal stimulation. This new approach offered the advantage over conventional self-healing of eliminating the needs for additional ingredients such as catalyst, monomer or special treatment of the fracture interface. Moreover, while self-healing systems that rely upon the addition of healing agent are capable of regaining mechanical strength only once, these new healable resins demonstrated the built-in capability to restore mechanical properties several times through multiple cycles of healing. This allowed multiple damages occurring at the same location to be “repaired”. Then, depending on the damage suffered, the restored properties of the material (in particular the stiffness) was very close to that of the virgin material.
It was demonstrated that the developed automated self-monitoring built-in systems could have a multi-level role. It could act as a “trigger mechanism” allowing the discrimination of defects and material failure in a timely manner and be smart enough to compute the degree of malfunction and to assess autonomously in an active and remote mode whether aircraft structures needs the intervention of a “self-healing recovery program” for rapid repair and redeployment, allowing, therefore, continued aircraft operation. But it also allowed the evaluation of the restored properties following the healing process.
The major results of this project demonstrated that an advancement of the TRL of the concepts embodied by the proposed Material State Evaluation and Restoring System could result in a significant increase in aircraft life, passenger safety, and operating time while contributing to substantial cost savings through optimised quality control and maintenance system and will pave the way toward the recycling of composite materials
Project Context and Objectives:
Project Context

To meet the challenging environmental targets for 2020 set by the Advisory Council for Aeronautical Research in Europe (ACARE) radical changes in current aircraft design rules and philosophy must be implemented. The four goals to be achieved by 2020 are:
o 50% cut in CO2 emission per passenger/km
o 50% cut in perceived aircraft noise
o 80% cut in nitrous oxide (NOx) emissions
o a greener life cycle
According to ACARE to achieve a 50% cut in CO2, step-change technologies must be developed. The airframe will contribute 20 to 25% of CO2 reduction. The most promising technologies identified were intelligent low-weight structures, improved aerodynamic efficiency, better manufacturing and recycling processes.
Possible breakthroughs identified were through novel and reliable tools, materials, techniques able to increase the efficiency of aircraft maintenance operation, extending the damage tolerance boundaries of materials (and therefore lighter material), reduced materials usage and extension of the service life of operating structures.
The industrial landscape was naturally converging towards the development and implementation of more accurate autonomous system with modular intelligent functions where automatic/self-monitoring and self-healing concepts are intrinsically linked.

Project Aims and objectives

Against the highlighted context, the aim of the project was to develop an autonomous modular system for Material State Evaluation and Restoring System (MSERS) of aircraft structures leading to continuously known (and restored) material health and demonstrate its efficiency in a life-cycle simulated environment starting from the production to a lab environment full operation, as shown in Figure 1.1 where relationship between the aircraft life-cycle, damage severity, aircraft materials and the proposed MSERS is presented.
This proposed built-in autonomous dual integrated system aimed to resemble biological systems in which malfunctions are automatically detected and a consequent autonomic healing response is triggered.
With the overall framework of the proposed aim, the objectives of the project were:

• Develop and optimize a new advanced concept for smart inspection and maintenance by employing Nonlinear Elastic Wave Spectroscopy (NEWS) technology in the development of Nonlinear Imaging (NIM) systems for the detection early stage damage/defects detection during manufacturing and in-service load of aerostructures and assessment of the quality of the proposed self-repair technique.
• Develop a self-healing concept based on thermo-reversible matrix coupled to shape memory effect that deliberately uses multiple repair mechanisms, with improved healing efficiencies and system robustness and assess the degree of recovery of the mechanical properties for the failure scenario to be investigated.

• Develop a self-healing composite based on ionized polymers doped with charges and embedded in HM fibers that combines high strength with a thermally activated multiple-repair healing concept upon detection of local and minor defects. The project will give the necessary insight of the effects of nano-charges in existing self-healing systems, while at the same time developing a new type of fiber reinforced self-healing nano-composite and development of techniques and methods to determine self-healing capabilities.

• Perform the first pioneering steps to integrate automated-monitoring and self-healing concept in a quality control inspection system and a Material State Evaluation and Restoring system (MSERS) for creating a revolutionary “Repair-and-Go” philosophy.

• Prepare the necessary grounds for the development of a life-cycle modular ‘automated -inspecting’ system prototype to allow quick, reliable and sensitive defects and damage evaluation, and to exhibit its applicability to real time in-situ inspection on the ground.

By providing early precursors signs of possible failures in a timely manner and by computing in a clear and smart way the location and morphology of degree of abnormal material behaviour, NEWS based imaging system will automatically assess whether the aerostructures require intervention by a “recovery program” and will also provide the mean to estimate the level and efficiency of the repairing process.

Due to the extreme sensitivity and reliability in detecting defects, damage precursors, and accumulated damage, NEWS techniques were assessed as potential solution for a step-change choice for accurate material state evaluation of airframes. The improved efficiency in localization and quantification of material “wounds” could allow the automatic activation and evaluation of a self-repair mechanism through in-situ thermally activation of reversible crosslinked polymers based composites and ionomers coupled to a shape memory effect/polymer.
To achieve the proposed aim and objective the project was divided in 8 workpackages. The objectives for each WP are reported below:

Work-package 1: Requirements and Manufacturing

• Design and manufacturing of test samples and components
• Identification of current NDT Issues and requirements
• Preparation of self-healing thermoreversible polymer and identification of the precursors and development of the synthesis procedure and shape memory polymers.
• Evaluation of self-healing efficiency of the thermoreversible matrix
• Preparation, evaluation of self-healing properties of new ionomer based composite using ionomers, nano-charges, and glass and HM fibers.
• Manufacturing of carbon fiber reinforced composites with and without self-healing

Work-package 2: Development and optimisation of experimental techniques for nonlinear imaging

• Development of sub-surface NEWS based imaging techniques to non-intrusively detect and map defects
• Development of surface NEWS based imaging techniques to detect front and back-surface structural anomalies
• Development of NEWS based experimental techniques and methodologies to obtain Nonlinear Images of complex aeronautical structures with localized damaged areas
• Optimisation of NEWS based imaging tools for automated monitoring and self-inspection
• Full field validation testing of the proposed NIM techniques

Work-package 3: Modelling support for NIM and self-repair

• Development and validation of 3D material models/ numerical codes for the study of elastic propagation waves in nonlinear homogeneous and heterogeneous materials with different kinds/level of nonlinearity and damage propagation under impact loading.
• Application of these models to support the development and optimization of NIM techniques (transducers positions, number of receivers, nonlinear signature to be used, etc.), e.g. by means of a theoretical analysis of Time Reversal and other invariances in nonlinear models and their link to the super-resolution effect.
• Application of the developed models to design novel imaging and/or processing techniques in terms of the technological requirements for transducers and driving electronics (WP4) and formulation of an experimental protocol for the validation of the novel methods.
• Formulation of hybrid methods i.e. use 3D codes as a new microimaging tool by coupling experimental measurements and computer simulations as a method for self-inspection.

Work-package 4: NIM Integration system

• Development and optimisation of transmitters/receivers for NIM techniques for simple structures, based on the feedback from other work packages, particularly with WP2 and WP5
• Development and optimisation of critical electronics and integration hardware for NIM techniques based on the feedback from WP2, WP3 and WP5
• Integration and construction of a modular set-up (system) capable of continuously imaging and monitoring the nonlinear signature in a given aeronautical complex structure
• Improvement of ultrasonic high-power excitation technique

Work-package 5: Development of data analysis tools for nonlinear imaging

• Development, validation and performance assessment of NIM data analysis, signal and image processing techniques for simple structures.
• Development of common basis for fusion of image data from several NIM techniques.
• Assessment of the effect of various environmental changes (experimental noise, temperature, humidity etc) on image quality and the development of improved imaging techniques.
• Efficient data management to optimise data storage, transfer and processing.
• Development, validation and performance assessment of advanced NIM imaging techniques for fast imaging and video compression of complex structures and materials.
• Construction of a user interface to facilitate in-situ imaging of industrial components
• Data classification integrated with the user interface via a web link

Work-package 6: Life-cycle Assessment and Validation of the Material State Evaluation and Restoring system

• Perform standard NDT on the test samples and components for the identified failure scenarios.
• Development, test and optimisation of self-healing procedure based on the coupled shape memory effect and in-situ activated thermo-reversible polymers for the neat matrix and fiber reinforced composites in order to assess the strength recovery efficiency
• Comparison of the sensitivity and reliability of NIM techniques with conventional linear imaging techniques and their capability to assess damage and the proposed self-repair technique
• Correctly assess the potential of the new technology and highlight in a measurable manner the improvement of NIM with respect to traditional NDT approaches.
• Combine the improved NIM technology with the improved SH material concepts in order to develop a knowledge base with which to rank Self Healing Composite concepts. This knowledge base would be of extremely high value to the aerospace industry in its search for cheaper yet reliable material solutions for aircraft fuselages

Work-package 7: Dissemination, Training, Exploitation and IPR management

• Disseminating knowledge on ALAMSA techniques throughout Europe and beyond
• Preparation of joint publications, organisation of workshops and International Conference
• Education of personnel at universities and NDT and Material research centres
• Tentative design of standard recommendations for the use of NIM imaging techniques
• Prepare an exploitation plan of the NIM system
• To manage Intellectual Property Rights (IPR) and knowledge ownership.
• Preparation of patents and granting licenses

Work-package 8: Project Management

• Realisation of an efficient plan for management of the ALAMSA project.
• Manage the financial, legal and administrative evolution of the project.
• Maintain a transparent status towards the EU about the progress of the project.
• To plan, organise, and review all consortium activities. To co-ordinate participant activities such that a durable, optimum structure is established.
• To assist participants and work package leaders to achieve their objectives.
• To create communication strategy to report to the EC and project committee, monitor plans and operational performance of all activities.
• To review, control and report financial information (budget and costs) to the consortium and the EC.
• Maintenance of the consortium agreement

Project Results:
In this section the major results of the two main scientific and technological topics, automated monitoring using nonlinear acoustic methods and the self-healing materials will be presented.
Self-healing Material Concept Developments and Characterisation

In the framework of the ALAMSA project the partners have developed three concepts for multiple self-healing in fibre composites; namely:
a) self-healing epoxy,
b) induction activated self-healing ionomers, and
c) compartmented fibres.
Two of these concepts, capable of multiple healing events, were up-scaled and used to create complex structures. While self-healing epoxies are developed to heal damages both as resin matrix of reinforced composite and as adhesive layer for T-joints, ionomers were used to act as healable interlayers. Both concepts were explored and related to on-demand temperature triggered repeatable healing.
The two major partners involved in the development of self-repair concepts based on self-healing mechanism were the TU Delft and IPCB.
Within the ALAMSA project the TU Delft team focused on the development of two different concepts for self-healing composites:
o Ionomer based interlayers capable of localized healing upon inductive heating
o Encapsulation of external healing agent by alginate based compartmented fibres
1) The study on ionomer interlayers within the ALAMSA project showed that damage can be healed by localized heating upon the application of an inductive field. Such an approach allows on demand localized heating leading to healing of damages or manufacturing defects. It is believed that this is a major step towards the application of intrinsic self-healing polymers in composite structures as the requirement of large scale ovens to fit large panels and/or structures is no longer necessary. Within the project, the obtained knowledge on the healing of ionomers was used to introduce and heal delaminations within CFRP-ionomer composite sandwich laminates. The healing of these delaminations was monitored with NDT. Due to the extensive expertise that was available within the ALAMSA consortium the impact and importance of combining self-healing and NDT technology was clearly shown. Being able to determine the extent and effect of healing on the mechanical properties of a composite in a non-destructive manner is a key requirement for application. As such, the findings within this project bring the use of self-healing materials in actual composite structures one step closer.
Due to the outcomes of the ALAMSA project, the TU Delft has decided to continue their efforts on further developing both self-healing strategies (compartmented fibres and induction heating) with the aim to direct them towards final applications.
2) The compartmented fibre concept showed clearly potential to heal cracks and this will be further advanced by TUDELFT in the future with its own funding. It is believed that the use of alginate based compartmented fibres in addition to heal delaminations that are created upon impact will act as impact energy absorbers. Nowadays, the compression after impact (CAI) properties of composite materials is considered as the main factor taken into account when certifying aerospace composite structures. Due to a combination of healing and an increased impact resistance, the compartmented fibre technology has the potential to increase the CAI properties of glass and carbon fibre reinforced polymer composites. As a result, the over-dimensioning of composite materials can be reduced (thinner panels would be required) leading to a reduction in material, fuel and environmental costs.
Only the most important results are reported here. In the following figure it is clearly shown how the healing takes place as a function of time in a delaminated region of a CFRP-ionomer composite sandwich panels Figure 1 ( the initial blue area becomes smaller and smaller).

Figure 1 Healing of the 5cm soft-soft delaminated CFRP-ionomer laminate over time monitored.

Compression experiments were performed on specimen with, without and healed delaminations to show the effect of damage and healing on the mechanical properties of the composites. The resulting compression curves are shown in Figure 2.

From this figure it is clearly seen that the introduction of a delamination within the thermoplastic layer leads to an onset of failure at lower compressive strengths. After healing an increase in the ultimate compressive strength was observed.

Figure 2 Compression curves for CFRP-ionomer composites with a 5 cm delamination. Partial restoration of the compressive strength is shown after healing.

IPCB was involved in the ALAMSA project with the following tasks:
1. Development of thermosetting resin with self-healing ability.
2. Assessment of multiple self-healing ability.
Both tasks were completed successfully, and the major result is the availability of an epoxy resin with intrinsic self-healing capability, to be used as matrix for carbon fiber reinforced composite and as adhesive in complex geometry samples representative of the aeronautic applications. The major results can be easily visualised by looking at an example of the multiple healing efficiency demonstrated in Figure 3. The material was fractured (solid curve), then went through first healing and fractured again (healing 1), then went through second healing and fractured again (healing 2), and finally went through the final healing and fractured again (healing 3). The results clearly demonstrate that the material was capable of recovering the stiffness and most of the strength.
The work carried out on the healing concept was demonstrated both on small samples and aerospace components. Detailed discussions and technical aspects of the self-healing materials developed within the frame of this project can be found in the deliverables : WP1.D2 Precursors moieities and polymer structure identification, WP1.D3 Synthesis of Diels-Alder thermo-reversible systems, WP1.D4 Synthesis of ionomer nano-composites reversible resin, WP1.D5 Assessment of the self-healing efficiency of neat matrices, WP1.D6: Design and manufacturing of complex test components including multiple self-healing.

Figure 3 – Stress-Strain Multiple-Healing Example
Nonlinear Imaging Techniques

Various Nonlinear Imaging techniques were developed and optimised over the four year period. The development of these techniques was supported by numerical simulations that allowed from one side the understanding of the fundamental physics of the nonlinear acoustic phenomena, then from the other side these simulation allowed to optimise the techniques and interpret the results obtained. The modelling work advanced the state of the art of nonlinear acoustic simulations and only some of the major results are listed below:
• New material models were derived for the description of wave propagation in samples containing internal contacts (e.g. cracks, delaminations, debondings, imperfect intergranular joints) of known geometry with postulated contact interaction laws including friction. These material models were implemented in commercial codes such as LS-DYNA3D and COMSOL Multiphysics. We have confirmed the potential of the model to study different applications related to solids with cracks showing acoustic nonlinearity by means of illustrative examples. These codes can be considered as a major breakthrough in the field of ultrasonic inspection of materials with microcracks.
• (Time Reversal model support) Virtual experiments were performed to optimize Time Reversal based NIM techniques and experimental setups. Time reversal techniques allow focusing of high levels of energy in small areas, and are consequently very useful for the local activation of defected zones. Numerical simulations show the potential of a combination consisting of dual energy reciprocal time reversal and nonlinearity filtering using the scaling subtraction method. The results showed that that the nonlinear response at the surface is linked to an effective nonlinearity within the medium based on the defect geometry and the distribution of the local stresses.
• A hybrid TR NIM procedure, mixing experimental and numerical analysis, were developed defined in view of the self-inspection capabilities of TR based NIM methods, and a new methodology was developed with the purpose of generating “reference” signals, which may be used for selective focusing. Emphasis is given to the reconstruction of smaller sources in the presence of larger ones. Inherent limitations of the traditional time reversal imaging technique in the case of multiple damaged locations make it difficult to distinguish the individual damaged area, only the “larger” ones become evident masking the “smaller” ones. We developed a selective source reduction (SSR) method which employs a subtraction technique to selectively suppress in amplitude (and ideally eliminate) a time reversed focal signal that is masking another damaged area. We showed by means of 2D wave propagation simulations that the new method can be applied iteratively to successfully image multiple masked nonlinear defects.
• (Sparse Array (RAPID) model support)
A hybrid Time Reversal procedure, mixing experimental and numerical analysis, was developed in view of the self-inspection capabilities of one of the NIM methods (RAPID). The new procedure allows to obtain an environmental independent baseline signal selection process by performing the signal recording at two amplitude levels. As such the RAPID method is transformed into a baseline-free method. This eliminates the requirement for an intact baseline signal which should improve the real-world applicability of RAPID. A detailed description of all the simulation work is reported in the individual deliverables: WP3.D1 WP3.D2 WP3.D3 WP3.D4 WP3.D5
Various Nonlinear Imaging techniques were developed and optimised over the four year period. The detailed discussion of descriptions of the techniques, the development phase, data analysis tool software development can be found in the deliverables of WP2 , WP4, and WP5.
Among the full Field-testing of the Nonlinear Imaging techniques developed it is worth mentioning:
• (Resonant Nonlinear Imaging of Defects – RENIM);

The basic concept behind this method is that by exciting a local resonance of defect (LDR) a high vertical displacement is excited at the damage location. Various modifications of this technique were developed such as noncontact RENIM by using LDR laser vibrometry (RESLV) and so on. By exciting the local resonance as shown Figure 4, nonlinear clapping between opposite crack faces occurs generating nonlinear elastic wave that can be picked by a set of transducers.

Figure 4 – Local Defect Resonance (LDR)

An automatic detection algorithm to successfully identify the LDR frequencies for all available types of defects and materials was developed. The algorithm is coupled to an iterative sizing routine that is capable of estimating the size of an equivalent circular defect. The equivalent circular defect was used as an idealization of a real defect shape and size based on the expected distribution of the fundamental LDR mode shape. The methodology was verified by carrying out several measurements on different samples, e.g. sandwich composite, GFRP, ionomer composite, that contain various type of damage, such as delaminations or disbonds. Moreover, it was demonstrated that the LDR mode frequency and shape is independent of the boundary conditions (BC) and the source location up to the measurement error.
Full scale RENIM testing of various defects (delaminations, impacts, disbonds) in realistic composite structures was carried out and demonstrated reliable nonlinear imaging at moderate input power, enhancement of efficiency, sensitivity and overall quality of nonlinear imaging of defects. Moreover, the use of RENIM in NDT of delaminations shows that the method is capable of not only imaging of the defects, but could also be used for estimation of their sizes and gravity of defects based on measurements of LDR frequencies. Multiple images of defects (higher harmonic, sub-harmonic frequency components) obtained from a single nonlinear imaging test by using RESLV demonstrate an enhanced probability of their detection and an increased signal-to-noise ratio of nonlinear images. Overall RENIM testing results proved to image of various defects in composite materials and aviation structures of large sizes (m-scale) and complicated shapes (angled and step thickness panels, T-shape stringer components, spar-ribs combinations, stiffened panel) as shown in Figure 5.

Figure 5-RENIM Imaging of damage on a stringer-skin connection

Figure 6-RENIM Imaging of damage on a stiffened panel
• Nonlinear Phased array. Various techniques employing phased array system were developed. The most promising one were

o Nonlinear ultrasound cross correlation technique

Nonlinear ultrasound cross correlation (NUCC) method, for the detection and imaging of material defects/damage in simple and complex composite structures, relies on a post-process technique that determines the cross correlation between frequency components extracted from spectrogram analysis of individual array element responses. The process allows for the focus on individual frequency components in time, due to the spectrogram analysis. This allows for the evaluation of nonlinear effects in the output signals and enables the determination of linear and nonlinear responses when testing was conducted. The effectiveness of the proposed method to isolate and assess harmonic information is clearly observed on two composite structures (a 90 degrees’ panel and flat composite plate) with embedded defects. The ability of the nonlinear responses to evaluate defects was also demonstrated.
o Constructive nonlinear array (CNA) technique

A Constructive Nonlinear Array (CNA) technique was proposed for the detection of defects/damages in complex composite structures. This method relies on a post-process technique that phase-matches and constructively sums signals captured at multiple grid positions given multiple transmitting positions. The results show that the method increases accuracy and repeatability of nonlinear imaging techniques (NIM). The main reason for this is the hypothesis of diminishing equipment harmonics given an array of increasing transmit positions, which has been demonstrated experimentally. An example of imaging damage is shown in Figure 7.

Figure 7 – Imaging damage using a Constructive nonlinear array (CNA) technique
• Nonlinear Stimulated Thermography.

This method is based by observing high heat generation at crack location when nonlinear elastic waves are generated using an ultrasonic stimulation. An example of the techniques is shown in Figure 9. The technique was capable of detecting multiple damages in 72sec. This technique would be ideal for quick scan and detecting sub-surface damages or delaminations in composite materials.

a) b)
Figure 9 a) Linear C-Scan b) Nonlinear stimulated thermography

• Linear and Nonlinear Reconstruction Algorithm for Probabilistic Inspection of Damage
Reconstruction Algorithm for Probabilistic Inspection of Damage (RAPID) is a Lamb wave based imaging technique that uses information gathered by a sparse array (network) of transducers to create a probability map of defects. A new concept for a RAPID nonlinear Lamb wave based imaging technique was proposed. This free-baseline imaging was evaluated by the RAPID technique in combination with three nonlinearity parameters including the high-low signal correlation coefficient, the energy of the SSM signals and the third harmonic ratio. The results demonstrate the potential of this technique in estimating the damage location with an acceptable error (smaller than 1 cm) for each of the considered parameters. It was found, among others things, that all three nonlinearity parameters exhibited sufficient damage sensitivity, and that the high-low signal correlation coefficient and the energy of the SSM signals are most sensitive to phase shifts in the signal (Figure 8).

Figure 8- Guided wave tomography using RAPID algorithm
Some of these techniques were also used to monitor the recovery of the health of self-healed samples. An example is shown in Figure 1.
It is worth mentioning that to prove all these techniques a wide variety of materials, size, layup, and complexity were manufactured by the major industrial partners. These were typical samples and components used in commercial aircraft and structural change/damage was introduced to simulate real scenarios that are expected to occur during the life of an aircraft. The techniques were compared to standard industrial inspection procedure. The results showed that for some particular type of damage the NIM were capable of clearly detecting and image damage while linear ultrasonic method failed. An example of this is shown in Figure 6. These samples were manufactured by Spirit Aerosystems and tested using their industrial linear ultrasonic equipment (Figure 4a). As shown in Figure 4b and Figure 4c, two of the developed techniques were clearly capable of imaging the damage.

a) b) c)
Figure 10 Comparison between a standard industrial linear inspecting and NIM techniques – a) Linear Ultrasonic b) NIM NACU 200kHz transmission c) NIM-Nonlinear laser scanning vibrometry

In conclusion, the development of these NIM techniques was gradual and allowed a clear advancement of self-inspections techniques. The techniques were developed and tested on small samples, small coupon and then full scale component and proved in a simulated industrial environment. Some of the technique reached a Technology Readiness Level of 6 while some as reported in the exploitation section are already commercialized, hence a Technology Readiness Level of 9 was achieved.

Potential Impact:
ALAMSA provided an opportunity for the PI and the research team to become world leaders in the science of nonlinear acoustic/ultrasonic and self-healing. The research work undertaken during ALAMSA project posed the basis for developing and funding novel research activities, thus levering the strength of current ultrasonic and thermographic systems. As an example, funding were granted from the National Nuclear Laboratory for detecting cracks in steel container, Dr. Ciampa was recently funded an EPSRC First Grant project (“NUSIT”, EP/N016386/1, £125k) focused on the development of a NDE imaging method based on a combination of nonlinear ultrasonic methods and thermography.

Both the UK and Europe are committed to increasing safety and reducing CO2 and NOx emissions. Results from ALAMSA helped delivering such commitments. The PI collaborated with the University’s Institute for Policy Research links in relation to its policy challenge of “Resourcing the Future”, and engaged with policy makers in the air transport showing how ALAMSA supported the commitments of reducing CO2 and NOx emissions.

The SMEs involved in the project are all long established companies with proven track records of business development. The developments of technological techniques/devices ensured the technological success and commercial exploitation for SMEs (See exploitation Section). It is clear that the participating SMEs are, after the termination of the project, capable to offer their newly developed skills/tools with regard to the supply chain to potential customers. In such respect, the ALAMSA project has enlarged their field of competences by new know-how and experience in very special fields and most important new product lines to be sold.

On the other hand, the PhDs and PDRAs involved in the project had the opportunity to develop unique skills in NDE technology, numerical simulations and signal processing, material science. A significant number of students attended training courses and workshops at the various universities involved ( an example is the University of Bath course “Effective communication skills for researchers”) to fully support their professional development. This will allow future generations of engineers to be ready to help the European industries in meeting the high demand of skilled and capable engineers and scientists.

It is known that aerospace structures have one of the highest payoffs for maintenance inspection applications since damage can lead to catastrophic and expensive failures and the vehicles involved are required to undergo regular costly inspections. The introduction of a new inspection method combining enhanced microdamage sensitivity with smart sensing systems are breakthrough technologies allowing quality control of damaged/undamaged parts and safety of products that are of major importance (a market that is hundreds of billions of Euros per year), therefore the future potential economic benefit to the aeronautics industry within Europe is huge.

It was demonstrated that for some specific type of damage maintenance cost could be substantially reduced and in the future could lead to an increased product reliability through the use of automated systems, hence profit can increase accordingly. This project demonstrated that with further advancement of TRL of the methods proposed in ALAMSA will thus achieve two aims simultaneously, namely improve safety, quality and productivity and at the same time provide a relative decrease in direct and indirect costs by strongly reducing inspection times and costs, and increasing safe inspection intervals. In conclusion, it is obvious that this project fulfils the societal and policy objectives regarding life-cycle reduction cost of aircrafts, reduced waste and improved use of resources.

Dissemination Activities

The main results of the dissemination activities are reported below:

Attending international conferences and dissemination activities

ALAMSA-developed approaches to nonlinear testing and defect imaging, coupled to self-healing technologies have aroused considerable interest in the world NDT and new materials communities. The partners of the ALAMSA consortium have received multiple invitations to high-profile international congresses and conferences in Europe and overseas to deliver invited and plenary talks. These international scientific events included more than 50 forums, like World Congress on NDT, European conference on composite materials, International conference on advanced composite materials, International congress on ultrasonics, European conference on NDT, International conference of the Institute of Electrical and Electronics Engineers (IEEE), etc. Total number of conference proceedings publications over the project duration is 49. Majority of them enjoyed open access policy and have been integrated into existing reporting lines of funding agencies of the European Commission by uploading to ZENODO website (34 publications).
ALAMSA dissemination activities included 104 events which comprise such highlights as 2 radio interviews to BBC radio with million-scale audience and numerous oral presentations at aerospace- and new material-related meetings.

Writing papers in international reviewed journals

The findings of the ALAMSA project have been widely published in internationally reviewed scientific/technical journals. Overall number of peer-reviewed papers published over 4 year project is 35, i.e. more than 8 papers per year. However, more than 15 extra paper have been submitted and will be published in the near future. The periodicals of the publications included top-ranked journals on polymers and on-destructive testing and evaluation (NDT, NDE): Research in NDE, NDT&E International, the Journal of Acoustical Society of America, Ultrasonics, Journal of NDE, etc. The full list of the publications can be found in a deliverables of WP7.

Organizing special NIM sessions at NDT meetings/exhibitions

Another acknowledgement of the interest and importance of the ALAMSA-obtained results is concerned with organizing special sessions and conferences on the topics related to nonlinear NDT and imaging. E.g. a special session on nonlinear methods in NDT and materials characterization was held at the International Symposium on non-destructive characterisation of materials organised by the Aerospace Corporation (Los Angeles). The ALAMSA partners have also organized a special session on Nonlinear NDE/NDT at International Congress on Ultrasound, Metz, France and the 20th International Conference on Nonlinear Elasticity in Materials (ICNEM20) in Bruges, Belgium.

Organizing university classes/short courses/student projects

The results of ALAMSA project have also been widely used in academic activities of the ALAMSA university partners.
An annual course on nonlinear ultrasonics is delivered for the students EC Lille.
Weekly seminars on physical and nonlinear acoustics for PhD students are held in in Spring semester at KU Leuven. In particular, some results were presented by Prof. Koen van den Abeele, KULeuven, in two seminars on nonlinear acoustics to the Masters Course in Physics: Physical Acoustics (B-KUL-G0J31A). The basis of acoustic wave propagation in fluids is reviewed, together with an introduction in the tools, terminology and conventions in acoustic signal analysis.
A short course on nonlinear NDT and NIM was delivered at the IEEE Ultrasonic symposium in Chicago by IKT-ZFP.

In addition, 5 PhD dissertations and 1 Master thesis on the methods developed in the framework of ALAMSA thesis have been implemented over the course of the project.

The results obtained in the ALAMSA project were also presented to MSc students in the 3ECTS course "Self-Healing Materials" of the Faculty of Aerospace Engineering at the TUDelft. This course is held every year and led by Dr Santiago J. Garcia.
Academic activities on dissemination of the ALAMSA methodology included also student projects in Germany, Belgium, UK and some university classes in Italy.
Creating an information leaflet and maintaining a web-page

An information leaflet on ALAMSA was created and supported by the University of Bath over the project duration. A web site has been constructed, explaining the objectives and reporting the achievements of the project. The web-site contained a transparent part opened to the public, and a restricted part for all partners. The latter served as a main channel for communication and file exchange between the project partners.
The UBATH also created an online information leaflet and the web-page was located at go.bath.ac.uk/alamsa.

EXPLOITATION

Exploitation was crucial to use all knowledge gained within ALAMSA and the partners made all the attempts to transfer it to market values. Most of the partners were involved in the development of tools/techniques that eventually allowed important technological transfer to commercial product or future opportunities. In this process, clearly the SMEs played a significant role in the transfer process. The major exploitation results are below reported:
1) Edevis has already started to exploit sub-solutions from ALAMSA project introducing non-linear Shearography system (VibroShearoVis).

2) Thermography with LDR effective excitation will follow into an EDEVIS product (VibroThermoVis).
3) Full integration of Local Defect Resonance excitation techniques into Edevis standard products has been started and is continuously improved.

4) Development of highly mobile system based on Local Defect Resonance with thermography

5) OEM modules based on Local Defect Resonance for integrators
6) Together with BMW central laboratory in Munich EDEVIS will also be involved in development of test device for automotive applications based on low power LDR acoustic thermography (B2B project, no public funding).
Future commercial opportunity for Edevis downstream the project are:
- Extended marketing on thermography using LDR effect with broadband excitation (VibroThermoVis)
- Further research project to improve technology and optimize for highly mobile solutions (“Mobile ultrasonic thermography for imaging damage in composites”)
DAKEL was involved in the development of actuation and sensing technology based on the piezoelectric effect. The major achievement that have led to commercial opportunities are listed below:
1) A set of transducers with the new contact plate optimized for composites and the new damping layers to cancel reverberations were produced with various configurations and in several pieces each. These new transducers are going to be included in DAKEL’s commercial offer to customers needing special transducers for composites. This technology will also be used to modify some other transducers produced by DAKEL.

2) A 128-element linear phased array probe was produced, tested for reliability and accuracy on a number of samples. Another 32-element linear phased array probe was produced for testing purposes.

3) Development of a Part of an Acquisition System HW for signal transmission. Signal transmission hardware part of the DAKEL ZEDO, and it may turn any of the input acquisition channels of the device into a transmitting channel. It is not fully ready for application, yet. Hardware part was prepared within ALAMSA, the software needs yet to be done (outside the scope of ALAMSA). It can be exploited in the field of acoustic emission for on-line transducer testing and diagnostics.

Figure 11 – Acquisition Card

IPR management

The PI worked with the University of Bath’s Research Innovation Services to conduct a review of Intellectual Property (IP) developed in this project and, if applicable, to protect it through patent, copyright and design registration processes. Similar process was conducted by each partner. Commercial applications of nonlinear time reversal and nonlinear phased array, as well as spin-out opportunities were investigated during the project. Potential partners were sought through the ongoing collaborations with a number of collaborators such as AgustaWestland, Airbus, Rolls-Royce, the Nuclear National Laboratory and the industrial partners of the EU Horizon 2020 “EXTREME” project.
The IPR on ALAMSA results have been registered in 2 patents:
1. „System for nondestructive inspection of structural components” (IKT-ZFP jointly with Airbus Operations GmbH, European Patent Application No. 15162660-3)

2. “Berührungsloser und breibandiger akustischer Schalleintrag zur Anregung lokaler Schwingungsresonanzen von Materialschäden” (Detection of damage by using non-contact wideband acoustic excitation of local defect resonances), German patent application DE 10 2016 224 988.6.

List of Websites:
http://www.bath.ac.uk/ris/about/rpms/projects/alamsa/index.html

Final Report Summary - ALAMSA (A Life-cycle Autonomous Modular System for Aircraft Material State Evaluation and Restoring System)

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